Abstract
Feline injection site sarcomas (FISS) are malignant skin tumors with high recurrence rates despite the primary treatment of radical surgical resections. Adjunctive radiotherapy or chemotherapy with doxorubicin is mostly ineffective. Cellular and molecular causes of multidrug resistance, specific physio-chemical properties of solid tumors impairing drug transport, and the tumor microenvironment have been indicated for causing standard chemotherapy failure. Gold nanoparticles are promising imaging tools, nanotherapeutics, and drug delivery systems (DDS) for chemotherapeutics, improving drug transport within solid tumors. This study was conducted to assess the distribution of 4-nm glutathione-stabilized gold nanoparticles in FISS and their influence on kidney and liver parameters in nude mice. The role of gold nanoparticles as a doxorubicin DDS in FISS was examined to determine the potential reasons for failure to translate results from in vitro to in vivo studies. Grade III tumors characterized by a large area of necrosis at their core displayed positive immuneexpression of tumor-associated macrophages (TAM) at both the periphery and within the tumor core near the area of necrosis. Gold nanoparticles did not cause necrosis at the injection site and had no negative effect on liver and kidney parameters in nude mice. Gold nanoparticles accumulated in the tumor core and at the periphery and co-internalized with TAM—an important observation and potential therapeutic target warranting further investigation. The large area of necrosis and high immunoexpression of TAM, indicating “pro-tumor macrophages”, may be responsible for FISS tumor progression and therapeutic failure. However, further studies are required to test this hypothesis.
Highlights
Feline injection site sarcomas (FISS) are malignant solid tumors with a high recurrence rate despite performing radical surgery, which is the primary method of treatment
The sizes of the Au-GSH and Au-GSH-Dox particles determined using dynamic light scattering (DLS) and TEM method were different. This was the effect of surface modification of the gold nanoparticles by doxorubicin and glutathione
The maximum was located at ca. 520 nm (Figure 2)
Summary
Feline injection site sarcomas (FISS) are malignant solid tumors with a high recurrence rate (ranging from 14–69%) despite performing radical surgery (with 3–5 cm of “clean” margin), which is the primary method of treatment. Despite the cellular and molecular causes of multidrug resistance (MDR), the tumor microenvironment and specific physio-chemical properties of solid tumors that cause imperfect drug delivery and transport have been recently indicated as important causes of standard chemotherapy failure. Limited drug access results in drug concentrations that are too low in hypoxic cells, where most anticancer agents are less active [4,5]. This causes a vicious circle as hypoxia, which is an indicator of the malignant phenotype, is involved in up-regulating genes responsible for MDR, including ABCB1 encoding P-gp
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